A huge grass fire that blew smoke across the lanes of Highway 99 kept Ceres firefighters busy for nearly five hours on Sunday evening as Modesto firefighters had their hands full with a commercial fire in south Modesto.

The grass fire in Ceres was reported at 846 p.m. as it swept from Service Road west of Mitchell Road toward the freeway. Fire Captain Randy Wheeler said five to six acres of dry grass, stumps and trees along Highway 99 were scorched. Heavy smoke caused Highway 99 motorists to slow down for lack of visibility as the California Highway Patrol closed the northbound onramp at Mitchell Road.

"I was impressed that people did slow down on the freeway and slowed down single file in the number one lane," said Captain Wheeler.

Approximately 17 firefighters from Ceres, Keyes and Burbank Paradise fire department knocked down the blaze within 40 minutes but keeping on top of burning trees and stumps cost the crew nearly five hours of time.

Wheeler said that the cause of the fire could not be pinpointed but could have been started by someone discarding something out the window of a vehicle.

Earlier on Sunday, Modesto and Ceres firefighters fought a fire that damaged a 7,200-square-foot metal commercial building in the 300 block of W. Hatch Road west of Crows Landing Road. The building housed Falcon's Auto Repair and goods for the Spa Doctor. The building once housed California Muffler which was being used for business paperwork and tool storage.

The building is owned by Paul Caruso, the former county supervisor.

The fire broke out at 2:30 p.m. and drew approximately 30 firefighters.